JPWO2012077477A1 - Near-infrared reflective film and near-infrared reflector provided with the same - Google Patents

Abstract

A near-infrared reflective film having excellent near-infrared reflectivity and high transparency in the visible light region and having no visible light reflectance unevenness and a near-infrared reflector provided with the same are provided. A high refractive index layer containing a water-soluble polymer and metal oxide particles having a higher refractive index than the water-soluble polymer, a water-soluble polymer, and the water-soluble polymer. Two or more low refractive index layers containing metal oxide particles having a low refractive index are alternately laminated, and the total number of the high refractive index layer and the low refractive index layer is n, and n / When the total film thickness of the constituent layers from the region 2 to the substrate is Σd1, and the total film thickness of the constituent layers from the region n / 2 to the outermost layer is Σd2, the film thickness ratio Σd1 / Σd2 is 1.05 or more 1. A near-infrared reflective film, which is 1.80 or less.

Description

  The present invention relates to a near-infrared reflective film excellent in near-infrared reflectivity and visible light uniformity and a near-infrared reflector provided with the same.

  In order to reduce the electric energy of cooling operation in summer, energy-saving technology that suppresses the heat radiation energy of sunlight entering the room through the window glass of houses and offices has attracted attention in recent years. Various corresponding films have been evaluated.

  In these films, a film containing a pigment that absorbs near-infrared rays on the film, a system that absorbs near-infrared light, a system that reflects heat radiation energy by sputtering metal on the substrate surface, and layers having different refractive indexes Various systems have been proposed, such as a system in which interference is reflected by a laminate in which layers are alternately stacked.

  Among the methods proposed above, the method using a pigment that absorbs near infrared rays has a characteristic that the film itself has heat, and the method of sputtering a metal not only near infrared rays but also visible light, etc. Also has a characteristic of reflecting. On the other hand, a method using a laminate in which layers having different refractive indexes are alternately laminated can efficiently reflect only near infrared light, so that the film does not have heat and transmits visible light. Can be made. For this reason, the system using the laminated body which laminated | stacked the layer from which a refractive index differs alternately is a technique with high usefulness as a near-infrared reflective film for windows.

  In the method of alternately laminating layers having different refractive indexes, generally when reflecting light in the near infrared region, assuming that the wavelength of the light in the near infrared region is λ, the optical film thickness (refractive index of each layer). By setting the x physical film thickness to be λ / 4, light can be reflected around λ. In this case, the greater the number of film layers, the higher the reflectance in the vicinity of λ, but the smaller the wavelength width that can be reflected, and a sideband of a rumble-like reflection occurs around the main reflection, which is adjacent to the near infrared region. Strong interference reflection occurs in the visible light region. Therefore, simply increasing the number of layers of the laminate reduces the wavelength width that can be reflected, resulting in less effect of reflecting the radiant energy of sunlight, and increased interference in visible light. .

  In response to the above problems, a method of reflecting a wide range of wavelengths has been studied. For example, as a technique of an optical lens, a high refractive index thin film made of a high refractive index material and a low refractive index thin film made of a low refractive index material are alternately used. An infrared cut filter in which 16 to 32 layers are laminated on a transparent substrate, and the first layer and the second layer from the transparent substrate side have an optical film thickness of (λ / 4) or more. The third to sixth or seventh layers are formed with an optical film thickness of (λ / 4) or less from the transparent substrate side, and the layer between the seventh or eighth layer and the final layer is An infrared cut filter having an optical film thickness of (λ / 4) or more and a final layer having an optical film thickness of (λ / 4) or less has been proposed (see, for example, Patent Document 1). .

Japanese Patent No. 4404568

  However, in the method described in Patent Document 1, although reflection in the near-infrared region appears, the transmittance is drastically reduced from 550 nm to 750 nm as the wavelength region, so that the visible light transmittance is lowered. was there.

  In addition, when trying to form a film on a plastic film, cracks occurred when heating at the time of sputtering film formation or cooling to room temperature at the time of removal, and the film could not be used as it was. In addition, since the film thickness is complicated, it is difficult to obtain optimum conditions.

  Therefore, the present invention has a wide reflection in the near-infrared region, and further, a near-infrared reflective film having no unevenness in reflectance in the visible light region, and using a combination of an inorganic material and a water-soluble resin, It aims at providing the near-infrared reflective film which a crack does not produce at the time of film forming, and the near-infrared reflector provided with the same.

  The above object of the present invention is achieved by the following configurations.

  1. A high refractive index layer containing a water-soluble polymer and metal oxide particles having a refractive index higher than the refractive index of the water-soluble polymer, a water-soluble polymer, and a refractive index of the water-soluble polymer. A near-infrared reflective film having a structure in which two or more low-refractive-index layers containing metal oxide particles having a refractive index lower than the refractive index are alternately laminated, each comprising the high-refractive-index layer and the low-refractive-index layer The total number of refractive index layers is n, the total thickness of the constituent layers from the n / 2 region to the substrate is Σd1, and the total thickness of the constituent layers from the n / 2 region to the outermost layer is Σd2. The near-infrared reflective film is characterized in that the film thickness ratio Σd1 / Σd2 is 1.05 or more and 1.80 or less.

  2. 2. The near-infrared reflective film as described in 1 above, wherein the film thickness ratio Σd1 / Σd2 is 1.05 or more and 1.25 or less.

  3. A near-infrared reflector having the near-infrared reflective film described in 1 or 2 on at least one surface side of a substrate.

  According to the present invention, a near-infrared reflective film having wide reflection in the near-infrared region, high transparency in the visible light region, and having no visible light reflectance unevenness, and a near-infrared reflector provided with the same Could be provided.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventors have found that a high refractive index containing a water-soluble polymer and metal oxide particles having a refractive index higher than the refractive index of the water-soluble polymer on the substrate. A refractive index layer, a water-soluble polymer, and a low-refractive index layer containing metal oxide particles having a refractive index lower than the refractive index of the water-soluble polymer are alternately stacked. Infrared reflective film, wherein the total number of layers of the high refractive index layer and the low refractive index layer is n, and the total film thickness of the constituent layers from the n / 2 region to the substrate is Σd1, n / 2 When the total film thickness of the constituent layers from the region to the outermost layer is Σd2, the near-infrared reflective film is characterized in that the film thickness ratio Σd1 / Σd2 is 1.05 or more and 1.80 or less. Wide reflection in the outer region, high transparency in the visible light region, no visible light reflectivity It found to be able to realize the infrared-reflective films, and completed the invention.

  That is, from the viewpoint of widening the reflection region, it is only necessary to configure the thickness of each constituent layer to be different, and by setting the thickness ratio of each constituent layer within the conditions defined in the present invention, all high refractions are achieved. It is possible to obtain a wide range of reflection characteristics in the near-infrared region rather than configuring the refractive index layer or the low-refractive index layer with the same film thickness, and the entire visible light region without causing specific strong reflection in the visible light region. It became clear that it became a near-infrared reflective film provided with the excellent near-infrared reflectivity in which fine interference overlaps, and completed this invention.

  Hereinafter, the details of the near-infrared reflective film of the present invention will be described.

《Near-infrared reflective film》
The near-infrared reflective film of the present invention comprises a water-soluble polymer, a high refractive index layer containing metal oxide particles having a refractive index higher than the refractive index of the water-soluble polymer, and a water-soluble polymer. When a polymer and a low refractive index layer containing metal oxide particles having a refractive index lower than the refractive index of the water-soluble polymer are formed in an adjacent structure and this is formed as one unit, at least 2 units When the total number of layers of the high refractive index layer and the low refractive index layer is n, the substrate side is more than the position of n / 2, that is, the position of 1/2 of the total number of layers. When the total film thickness of the constituent layers (also referred to as lower layer areas) is Σd1, and the total film thickness of the constituent layers (also referred to as upper layer areas) from the reference position to the outermost layer is Σd2, the film thickness ratio Σd1 / Σd2 is It is 1.05 or more and 1.80 or less.

When the total number n of layers is an even number, the boundary between the lower layer region from layer ₁ to layer _{n / 2} and the upper layer region from layer _{(n / 2) +1} to layer _{n as} viewed from the substrate side The region (n / 2) is an interface between the layer _{n / 2} and the layer _{(n / 2) +1} . For example, when the total number of layers is 4, the first layer and the second layer in contact with the base material are the lower layer region (Σd1), and the third layer and the fourth layer are the upper layer region (Σd2). The interface between the second layer and the third layer becomes the boundary region (n / 2). When the total number n of layers is an odd number, the boundary region (n / n) is defined on the lower layer side of the layer corresponding to the boundary region (n / 2) with reference to the layer corresponding to the boundary region (n / 2). The total thickness of the constituent layers up to the base material excluding the layer corresponding to 2) is Σd1, and the layer corresponding to the boundary region (n / 2) on the upper layer side corresponding to the boundary region (n / 2) The total film thickness of the constituent layers up to the outermost layer excluding is defined as Σd2. For example, when the total number of layers is 5, the first layer and the second layer in contact with the base material are the lower layer region (Σd1), the third layer is the boundary region (n / 2), and the fourth layer The layer and the fifth layer are the upper layer region (Σd2).

  The total number of layers is measured by cross-sectional observation with an electron microscope. At this time, when the interface between the two layers cannot be clearly observed, the determination is made based on the metal oxide particles of the high refractive index layer included between the layers. That is, for the EDX profile in the thickness direction of the metal oxide particles of the high refractive index layer, the position where the count number of the metal oxide particles of the high refractive index layer with respect to the peak top is halved is the interface between the two layers. .

  In the present invention, at least two units composed of a high refractive index layer and a low refractive index layer are laminated, but the refractive index difference between the adjacent high refractive index layer and the low refractive index layer Is preferably 0.1 or more. Furthermore, as the optical characteristics of the near-infrared reflective film of the present invention, the transmittance in the visible light region shown in JIS R3106-1998 is 50% or more, and the reflectance is 50% in the wavelength region of 900 nm to 1400 nm. It is preferable to have a region that exceeds.

  In general, in the near-infrared reflective film, it is preferable to design a large difference in refractive index between the high refractive index layer and the low refractive index layer from the viewpoint of increasing the infrared reflectance with a small number of layers, In the present invention, at least two units composed of a high refractive index layer and a low refractive index layer are provided, and the difference in refractive index between the adjacent high refractive index layer and low refractive index layer is 0.1 or more. Is preferable, more preferably 0.3 or more, and still more preferably 0.4 or more.

  The reflectance in the specific wavelength region is determined by the difference in refractive index between two adjacent layers and the number of layers, and the larger the difference in refractive index, the same reflectance can be obtained with a smaller number of layers. The refractive index difference and the required number of layers can be calculated using commercially available optical design software. For example, in order to obtain an infrared reflectance of 90% or more, if the difference in refractive index is less than 0.1, it is necessary to laminate 20 or more layers, which not only lowers productivity but also scatters at the lamination interface. Becomes larger, the transparency is lowered, and it becomes very difficult to manufacture without failure. From the viewpoint of improving reflectivity and reducing the number of layers, there is no upper limit to the difference in refractive index, but the limit is substantially about 1.40.

  Next, the basic configuration outline of the near-infrared reflective film of the present invention will be described.

  The near-infrared reflective film of the present invention comprises a water-soluble polymer, a high refractive index layer containing metal oxide particles having a refractive index higher than the refractive index of the water-soluble polymer, and a water-soluble polymer. It has a configuration in which at least two units composed of a polymer and a low refractive index layer containing metal oxide particles having a refractive index lower than the refractive index of the water-soluble polymer are laminated. The range of the total number of layers of the near-infrared reflective film of the present invention is preferably 100 layers or less, that is, 50 units or less, more preferably 40 layers (20 units) or less, and further preferably 4 layers (2 units). ) 20 layers (10 units) or less.

  In the near-infrared reflective film of the present invention, the difference in refractive index between the adjacent high-refractive index layer and low-refractive index layer is preferably 0.1 or more. When each layer has a plurality of layers as described above, it is preferable that all refractive index layers satisfy the requirements defined in the present invention. However, the outermost layer and the lowermost layer may be configured outside the preferable requirements defined in the present invention.

  In the near-infrared reflective film of the present invention, it is preferable to add metal oxide particles to the high refractive index layer, and add metal oxide particles to both the high refractive index layer and the low refractive index layer. Is more preferable.

  In the present invention, the refractive index of each component can be determined according to the following method.

  The refractive indexes of the high refractive index layer and the low refractive index layer according to the present invention were prepared by preparing a sample in which a refractive index layer to be measured was coated on a substrate as a single layer, and cutting this sample into 10 cm × 10 cm. Thereafter, the refractive index is obtained according to the following method. That is, using a U-4000 type (manufactured by Hitachi, Ltd.) as a spectrophotometer, the surface opposite to the measurement surface of the sample (back surface) is roughened and then subjected to light absorption treatment with a black spray. To prevent reflection of light on the back surface, measure the reflectance in the visible light region (400 nm to 700 nm) at 25 points under the condition of regular reflection at 5 degrees, obtain an average value, and calculate the average refractive index from the measurement result. Or a method using an F20 tabletop film thickness measurement system (Filmmetrics film thickness refractive index measurement device).

  In addition, for the refractive index of the water-soluble polymer constituting the high refractive index layer or the low refractive index layer, a sample in which the water-soluble polymer to be measured was coated on the substrate as a single layer was prepared, and It can be determined in a similar manner.

  Regarding the refractive index of the metal oxide particles constituting the high refractive index layer or the low refractive index layer, the method B (immersion method using a microscope (Becke line method)) of JIS K7142 “Method for measuring refractive index of plastic” Can be measured based on As an immersion liquid used in JIS K7142, “Contact Liquid” manufactured by Shimadzu Device Manufacturing Co., Ltd. is used, and a polarizing microscope “Eclipse E600 POL” (Nikon Corporation) is used as a microscope.

  Further, regarding the thicknesses of the high refractive index layer and the low refractive index layer according to the present invention, the total thickness Σd1 of the constituent layers from the intermediate region to the base material, and the total thickness Σd2 of the constituent layers from the intermediate region to the outermost layer The cross section of the near-infrared reflective film formed by laminating the high refractive index layer and the low refractive index layer according to the present invention is trimmed and exposed, and then the cross section is observed using a scanning electron microscope By doing so, the film thickness of each layer and Σd1, Σd2 can be obtained.

(High refractive index layer)
The high refractive index layer according to the present invention includes a water-soluble polymer and metal oxide particles having a refractive index higher than that of the water-soluble polymer. When the high refractive index layer includes a plurality of types of water-soluble polymers and / or metal oxide particles, the component having the largest content is adopted as a refractive index comparison target.

  A preferable refractive index of the high refractive index layer is 1.80 to 2.50, more preferably 1.90 to 2.20.

  Moreover, the preferable film thickness of a high refractive index layer is 20 nm-1000 nm, More preferably, it is 50 nm-500 nm.

(Metal oxide particles)
The metal oxide particles used in the high refractive index layer according to the present invention have a high refractive index with respect to the water-soluble polymer constituting the high refractive index layer.

The metal oxide particles that can be used cannot be generally defined by the type of the water-soluble polymer to be applied, but the refractive index is usually 2.00 or more, preferably 2.00 or more, 3.00. It is as follows. The volume average particle diameter is usually 100 nm or less. Specifically, zirconium oxide (ZrO ₂ ), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), and the like can be given. Among these, it is preferable to use rutile type titanium oxide particles having a high refractive index.

<Rutyl type titanium oxide>
In general, titanium oxide particles are often used in a surface-treated state for the purpose of suppressing photocatalytic activity on the particle surface and improving dispersibility in a solvent or the like. For example, titanium oxide particles Known are those in which the surface is covered with a coating layer made of silica and the particle surface is negatively charged, and in which the coating layer made of aluminum oxide is formed and the surface is positively charged at pH 8-10. . In the present invention, it is preferable to use an aqueous sol of titanium oxide which has a pH of 1.0 to 3.0 and has a positive zeta potential and is not subjected to such surface treatment.

  The volume average particle diameter of the rutile titanium oxide particles according to the present invention is preferably 100 nm or less, more preferably 4 nm or more and 50 nm or less, and further preferably 4 nm or more and 30 nm or less. When the volume average particle size is less than 100 nm, it is preferable from the viewpoint of low haze and excellent visible light transmittance. The volume average particle size exceeding 100 nm is preferable because it can be suitably applied to the high refractive index layer.

  The volume average particle diameter of the rutile titanium oxide particles according to the present invention is the volume average particle diameter of primary particles or secondary particles dispersed in the medium, and the volume average particle diameter is obtained by a laser diffraction method. To do. The laser diffraction method is a method for detecting diffracted light and / or scattered light generated when a particle is irradiated with laser light. When a particle is irradiated with laser light, diffracted / scattered light is generated in various directions depending on the size of the particle. For example, if the particle size is about millimeter to micrometer, the diffracted / scattered light gathers on the traveling direction side of the irradiation laser, and the diffracted / scattered light becomes smaller as the particle size decreases from micrometer to nanometer. It spreads to the opposite side of the laser traveling direction. The laser diffraction method is a method for detecting the diffracted / scattered light by a sensor and analyzing the intensity distribution to obtain the particle size.

  Furthermore, the titanium oxide particles according to the present invention are preferably monodispersed. The monodispersion here means that the monodispersity obtained by the following formula is 40% or less. The particles are more preferably 30% or less, and particularly preferably 0.1 to 20%.

<Method for producing rutile type titanium oxide sol>
In the present invention, as a method for producing a near-infrared reflective film, when preparing an aqueous high refractive index layer coating solution, the rutile type titanium oxide has a pH of 1.0 or more and 3.0 or less, and titanium. It is preferable to use an aqueous titanium oxide sol in which the zeta potential of the particles is positive.

  Examples of a method for preparing a rutile type titanium oxide sol that can be used in the present invention include, for example, JP-A-63-17221, JP-A-7-819, JP-A-9-165218, and JP-A-11-43327. Reference can be made to the matters described in Japanese Patent Laid-Open Nos. 63-17221, 7-819, 9-165218, 11-43327, and the like.

  In addition, as for other methods for producing the rutile type titanium oxide according to the present invention, for example, “Titanium oxide-physical properties and applied technology”, Manabu Seino p255-258 (2000), Gihodo Publishing Co., Ltd. The method of the step (2) described in the paragraph numbers 0011 to 0023 can be referred to.

  In the production method according to the above step (2), titanium dioxide hydrate is treated with at least one basic compound selected from the group consisting of alkali metal hydroxides or alkaline earth metal hydroxides. After the step (1), the titanium dioxide dispersion obtained comprises a step (2) of treating with a carboxylic acid group-containing compound and an inorganic acid. In the present invention, an aqueous sol of rutile-type titanium oxide having a pH adjusted to 1.0 to 3.0 with the inorganic acid obtained in the step (2) can be used.

(Water-soluble polymer)
The water-soluble polymer applicable to the high refractive index layer according to the present invention is not particularly limited. For example, at least one kind selected from celluloses, thickening polysaccharides, polymers obtained by vinyl polymerization, and gelatin is used. It is preferable to contain a water-soluble polymer. The refractive index of the water-soluble polymer is preferably 1.50 or more and less than 2.00.

  The water-soluble polymer as used in the present invention is defined as a polymer that dissolves in water of 25 ° C. at 1.0% by mass or more, preferably 5.0% by mass or more.

<Cellulose>
As the celluloses that can be used in the present invention, water-soluble cellulose derivatives can be preferably used. For example, water-soluble cellulose derivatives such as carboxymethyl cellulose (cellulose carboxymethyl ether), methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Examples thereof include cellulose derivatives, carboxymethyl cellulose (cellulose carboxymethyl ether) and carboxyethyl cellulose which are carboxylic acid group-containing celluloses.

<Thickening polysaccharide>
The thickening polysaccharide that can be used in the present invention is not particularly limited, and for example, generally known natural simple polysaccharides, natural complex polysaccharides, synthetic simple polysaccharides, and synthetic complex polysaccharides can be used. . For details of these polysaccharides, reference can be made to “Biochemical Encyclopedia (2nd edition), Tokyo Chemical Doujinshi”, “Food Industry”, Vol. 31 (1988), p.

  The thickening polysaccharide referred to in the present invention is a saccharide polymer and has a number of hydrogen bonding groups in the molecule. Due to the difference in hydrogen bonding force between molecules depending on the temperature, it has the characteristic that the viscosity difference at low temperature and the viscosity at high temperature are large. When the metal oxide particles are added to the thickening polysaccharide, the viscosity is estimated to increase due to hydrogen bonding with the metal oxide particles at a low temperature. The viscosity increase width at 15 ° C. is preferably 1.0 mPa · s or more, more preferably 5.0 mPa · s or more, and further preferably 10.0 mPa · s or more.

  Examples of the thickening polysaccharide applicable to the present invention include galactan (eg, agarose, agaropectin, etc.), galactomannoglycan (eg, locust bean gum, guaran, etc.), xyloglucan (eg, tamarind gum, etc.), Glucomannoglycan (eg, salmon mannan, wood-derived glucomannan, xanthan gum, etc.), galactoglucomannoglycan (eg, softwood-derived glycan), arabinogalactoglycan (eg, soybean-derived glycan, microorganism-derived glycan, etc.), Red algae such as glucuronoglycan (for example, gellan gum), glycosaminoglycan (for example, hyaluronic acid, keratan sulfate, etc.), alginic acid and alginates, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan Derived from Natural polymeric polysaccharides, and the like. Among these, from the viewpoint of not reducing the dispersion stability of the metal oxide fine particles coexisting in the coating solution, a thickening polysaccharide whose structural unit does not have a carboxylic acid group or a sulfonic acid group is preferable. Examples of such thickening polysaccharides include pentoses such as L-arabitose, D-ribose, 2-deoxyribose and D-xylose, and hexoses such as D-glucose, D-fructose, D-mannose and D-galactose. It is preferable that it is a thickening polysaccharide which consists only of. Specifically, tamarind seed gum known as xyloglucan whose main chain is glucose and side chain is glucose, guar gum known as galactomannan whose main chain is mannose and side chain is glucose, cationized guar gum, Hydroxypropyl guar gum, locust bean gum, tara gum, and arabinogalactan whose main chain is galactose and whose side chain is arabinose can be preferably used. In the present invention, tamarind, guar gum, cationized guar gum, and hydroxypropyl guar gum are particularly preferable.

  In the present invention, it is further preferable to use two or more thickening polysaccharides in combination.

<Polymers obtained by vinyl polymerization>
As the water-soluble polymer applicable to the present invention, polymers obtained by vinyl polymerization can be used. For example, polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, or acrylic acid-acrylic ester Acrylic resins such as copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, Or styrene acrylic resin such as styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-sodium styrenesulfonate copolymer, styrene-2-hydroxyethyl acrylate copolymer, styrene-2-hydroxy Ethyl ak Relate-potassium styrenesulfonate copolymers, styrene-maleic acid copolymers and their salts. Among these, particularly preferable examples include polyvinyl alcohol, polyvinyl pyrrolidones, and copolymers containing the same.

  The weight average molecular weight of the water-soluble polymer is preferably 1,000 or more and 200,000 or less. Furthermore, 3,000 or more and 40,000 or less are more preferable. In this specification, the weight average molecular weight is determined by gel filtration column chromatography (GFC). Specifically, it is obtained from a calibration curve created from a standard sample using GPC101 (manufactured by Showa Denko KK). Note that pullulan is used as the standard sample.

  The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, polyvinyl alcohol with a cation-modified terminal, anion-modified polyvinyl alcohol with a terminal, and non-ion-modified polyvinyl terminal. Modified polyvinyl alcohol such as alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The degree of saponification is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide and the like. The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Anion-modified polyvinyl alcohol is, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-2060888, as described in JP-A-61-237681 and JP-A-63-330779, Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol. Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification.

  In the present invention, when using a polymer obtained by vinyl polymerization, a curing agent may be used. When the polymer obtained by vinyl polymerization is polyvinyl alcohol, boric acid and its salts and epoxy curing agents are preferred.

<gelatin>
In the high refractive index layer according to the present invention, gelatin can be used as the water-soluble polymer.

  As the gelatin applicable to the present invention, various gelatins that have been widely used in the field of silver halide photographic light-sensitive materials can be applied. For example, in addition to acid-processed gelatin and alkali-processed gelatin, production of gelatin is possible. Enzyme-treated gelatin and gelatin derivatives that undergo enzyme treatment in the process, that is, modified by treatment with a reagent that has an amino group, imino group, hydroxyl group, carboxyl group as a functional group in the molecule and a group obtained by reaction with it. You may have done. The general method for producing gelatin is well known and is described, for example, in T.W. H. James: The Theory of Photographic Process 4th. ed. Reference can be made to descriptions such as 1977 (Machillan) 55, Science Photo Handbook (above) 72-75 (Maruzen), Fundamentals of Photographic Engineering-Silver Salt Photographs 119-124 (Corona). Also, Research Disclosure Magazine Vol. 176, No. And gelatin described in Section IX of 17643 (December, 1978).

  One example of gelatin that can be applied to the present invention is low molecular weight gelatin or collagen peptide. The low molecular weight gelatin referred to in the present invention is a gelatin having a weight average molecular weight of 30,000 or less, preferably 2,000 to 30,000, more preferably 5,000 to 25,000. Further, the collagen peptide as used in the present invention is defined as a protein obtained by subjecting gelatin to a low molecular weight treatment so as not to cause a sol-gel change.

  Low molecular weight gelatin or collagen peptides are hydrolyzed by adding gelatin-degrading enzyme to a commonly used polymer gelatin aqueous solution having a weight average molecular weight of about 100,000, hydrolyzing by adding acid or alkali, and atmospheric pressure. It can be obtained by thermal decomposition by heating under or under pressure, decomposition by ultrasonic irradiation, or a combination of these methods.

  In the present invention, high molecular weight gelatin having a weight average molecular weight of 100,000 or more can also be used as one kind of gelatin, such as lime-processed gelatin, acid-processed gelatin, and alkali-processed gelatin.

  In the present invention, the weight average molecular weight and molecular weight distribution of gelatin can be measured, for example, by gel permeation chromatography (GPC method).

  Regarding the molecular weight of gelatin, see D.C. Lory and M.M. Vedrines, Proceedings of the 4th IAG Conference, Sept. 1983, p. 35, Takashi Ohno, Hiroyuki Kobayashi, Shinya Mizusawa, Journal of the Japan Photography Society, 47, 237 (1984), etc., α component (molecular weight about 100,000), which is a structural unit of collagen, its dimer The β component, which is a trimer thereof, the γ component which is a trimer thereof, the amphoteric component which is a monomer, and a low molecular weight component obtained by irregularly cutting these components.

  As the high molecular weight gelatin having a weight average molecular weight of 100,000 or more according to the present invention, among the above components, an α component (molecular weight of about 100,000) which is a structural unit of collagen, a β component which is a dimer thereof, three of them Gelatin mainly composed of a γ component as a monomer.

  Moreover, as a manufacturing method of the high molecular weight gelatin whose weight average molecular weight which concerns on this invention is 100,000 or more, the following method etc. are mentioned, for example.

  1) In the extraction operation during the production of gelatin, an extract in the early stage of extraction (low molecular weight component) is excluded by using an extract in the later stage of extraction.

  2) In the said manufacturing method, process temperature shall be less than 40 degreeC in the process from extraction to drying.

  3) The gelatin is dialyzed in cold water (15 ° C.).

  By using the above methods alone or in combination, a high molecular weight gelatin having a weight average molecular weight of 100,000 or more can be obtained.

  In the present invention, each of the water-soluble polymers is preferably contained in a range of 5.0% by mass or more and 50% by mass or less with respect to the total mass of the high refractive index layer, and is 10% by mass or more and 40% by mass. % Or less is more preferable. However, when using together with water-soluble polymer, for example, emulsion resin, it may contain 3.0 mass% or more. When the amount of the water-soluble polymer is small, the film surface is disturbed and the transparency tends to deteriorate during drying after coating the high refractive index layer. On the other hand, when the content is 50% by mass or less, the relative content of the metal oxide particles becomes appropriate, and it becomes easy to increase the refractive index difference between the high refractive index layer and the low refractive index layer.

(Low refractive index layer)
The low refractive index layer according to the present invention is characterized by containing a water-soluble polymer and metal oxide particles having a refractive index lower than that of the water-soluble polymer. It is preferable that the refractive index be at least 0.1 or lower. In addition, when a low refractive index layer contains multiple types of water-soluble polymer and / or metal oxide particle, the component with the largest content shall be respectively employ | adopted as a comparison object of refractive index.

  The low refractive index layer preferably has a refractive index of 1.6 or less, more preferably 1.10 to 1.60, and even more preferably 1.30 to 1.50.

  Moreover, the preferable film thickness of the low refractive index layer is preferably 20 nm to 800 nm, and more preferably 50 nm to 350 nm.

  The metal oxide particles used in the low refractive index layer according to the present invention have a low refractive index with respect to the water-soluble polymer constituting the low refractive index layer.

The metal oxide particles that can be used cannot be generally defined by the type of the water-soluble polymer to be applied, but the refractive index is preferably 1.05 or more and less than 1.50. Specifically, silicon oxide (SiO ₂ ) is preferably used, and acidic colloidal silica sol is particularly preferably used.

  The silicon oxide preferably has an average particle size of 100 nm or less. The average particle diameter of the silicon oxide dispersed in the primary particle state (particle diameter in the dispersion state before coating) is preferably 20 nm or less, more preferably 10 nm or less. From the viewpoint of low haze and excellent visible light permeability, the average particle size of the secondary particles is preferably 30 nm or less.

  The average particle size of the metal oxide particles according to the present invention is to observe the particles themselves or the particles appearing on the cross section and surface of the refractive index layer with an electron microscope, and measure the particle size of 1,000 arbitrary particles, It is obtained as its simple average value (number average). Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area.

  The water-soluble polymer used in the low refractive index layer is the same as the water-soluble polymer described in the high refractive index layer, that is, celluloses, thickening polysaccharides, polymers obtained by vinyl polymerization, It is preferable to contain at least one water-soluble polymer selected from gelatin. The water-soluble polymers used in the high-refractive index layer and the low-refractive index layer may be the same or different, but from the viewpoint of performing simultaneous multilayer coating, they should be the same water-soluble polymer. Is preferred. The refractive index of the water-soluble polymer is preferably 1.50 or more and less than 2.00.

[Other additives]
In the high refractive index layer and the low refractive index layer according to the present invention, various additives can be used as necessary.

<Amino acids with an isoelectric point of 6.5 or less>
The amino acid referred to in the present invention is a compound having an amino group and a carboxyl group in the same molecule, and may be any type of amino acid such as α-, β-, and γ-, but has an isoelectric point of 6.5 or less. It is an amino acid. Some amino acids have optical isomers, but in the present invention, there is no difference in effect due to optical isomers, and any isomer can be used alone or in racemic form.

  For a detailed explanation of the amino acids according to the present invention, reference can be made to the description on pages 268 to 270 of the Chemical Dictionary 1 Reprint (Kyoritsu Shuppan; issued in 1960).

  Specific examples of preferable amino acids include aspartic acid, glutamic acid, glycine, serine, and the like, and glycine and serine are particularly preferable.

  The isoelectric point of an amino acid means this pH value because an amino acid balances positive and negative charges in a molecule at a specific pH, and the overall charge becomes zero. In the present invention, amino acids having an isoelectric point of 6.5 or less are used. The isoelectric point of each amino acid can be determined by isoelectric focusing at a low ionic strength.

<Emulsion resin>
The high refractive index layer and the low refractive index layer according to the present invention preferably further contain an emulsion resin.

  The emulsion resin referred to in the present invention is resin fine particles obtained by emulsion-polymerizing an oil-soluble monomer in an aqueous solution containing a dispersant and using an initiator.

  The emulsion resin according to the present invention is obtained by mixing an oil-soluble monomer finely dispersed in an aqueous medium, for example, an oil-soluble monomer having an average particle size of about 0.01 to 2.0 μm with a dispersant. It can be obtained by emulsion polymerization.

  Examples of the oil-soluble monomer that is emulsion-polymerized with the above polymer dispersant include ethylene monomers such as acrylic acid esters, methacrylic acid esters, vinyl compounds, and styrene compounds, and single weights of diene compounds such as butadiene and isoprene. Examples thereof include an acrylic resin, a styrene-butadiene resin, an ethylene-vinyl acetate resin, and the like.

  Dispersants used during the polymerization of the emulsion generally include polyoxyoxy, other than low molecular weight dispersants such as alkyl sulfonates, alkyl benzene sulfonates, diethylamine, ethylenediamine, and quaternary ammonium salts. Examples thereof include polymer dispersants such as ethylene nonylphenyl ether, polyoxyethylene laurate ether, hydroxyethyl cellulose, and polyvinylpyrrolidone, and polymer dispersants having a hydroxyl group.

  The polymer dispersant containing a hydroxyl group is a polymer dispersant having a weight average molecular weight of 10,000 or more, and has a hydroxyl group substituted on the side chain or terminal. There is no fundamental difference in the polymer component of the resulting emulsion resin depending on the type of dispersant used, but when emulsion polymerization is performed using a polymer dispersant having a hydroxyl group, the presence of hydroxyl groups is present on at least the surface of fine particles. It is presumed that the chemical and physical properties of the emulsion are different from emulsion resins polymerized using other dispersants. Examples of the polymer dispersant containing a hydroxyl group include those obtained by copolymerization of 2-ethylhexyl acrylate with an acrylic polymer such as polyacrylic acid soda and polyacrylamide, polyethers such as polyethylene glycol and polypropylene glycol, and polyvinyl alcohol. Polyvinyl alcohol is particularly preferable.

  As the polyvinyl alcohol, in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol having an anionic group such as a carboxyl group, and silyl having a silyl group Modified polyvinyl alcohol such as modified polyvinyl alcohol is also included. Polyvinyl alcohol has a higher effect of suppressing the occurrence of cracks when forming the ink absorbing layer when the average degree of polymerization is higher, but when the average degree of polymerization is within 5000, the viscosity of the emulsion resin is not high, and at the time of production Easy to handle. Accordingly, the average degree of polymerization is preferably 300 to 5000, more preferably 1500 to 5000, and particularly preferably 3000 to 4500. The saponification degree of polyvinyl alcohol is preferably 70 to 100 mol%, more preferably 80 to 99.5 mol%.

<Other additives for each refractive index layer>
Various additives applicable to the high refractive index layer and the low refractive index layer according to the present invention are listed below. For example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, and JP-A-60-72785. No. 61-146591, JP-A-1-95091, JP-A-3-13376, etc., various surfactants of anion, cation or nonion, JP-A-59- 42993, 59-52689, 62-280069, 61-242871, and JP-A-4-219266, etc., whitening agents such as sulfuric acid, phosphoric acid, acetic acid, PH adjusters such as citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, lubricants such as diethylene glycol, preservatives, Antistatic agents, can also contain various known additives such as a matting agent.

〔Base material〕
The substrate applied to the near-infrared reflective film of the present invention is preferably a film support, and the film support may be transparent or opaque. Various resin films can be used as the film support, and polyolefin films (polyethylene, polypropylene, etc.), polyester films (polyethylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, cellulose acetate, etc. can be used. Preferably, it is a polyester film. Although it does not specifically limit as a polyester film (henceforth polyester), It is preferable that it is polyester which has the film formation property which has a dicarboxylic acid component and a diol component as main structural components. The main constituent dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylethanedicarboxylic acid, Examples thereof include cyclohexane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl thioether dicarboxylic acid, diphenyl ketone dicarboxylic acid, and phenylindane dicarboxylic acid. Examples of the diol component include ethylene glycol, propylene glycol, tetramethylene glycol, cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis ( 4-Hydroxyphenyl) sulfone, bisphenol fluorene hydroxyethyl ether, diethylene glycol, neopentyl glycol, hydroquinone, cyclohexanediol and the like. Among the polyesters having these as main constituent components, from the viewpoint of transparency, mechanical strength, dimensional stability, etc., dicarboxylic acid components such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, diol components such as ethylene glycol and 1 Polyester having 1,4-cyclohexanedimethanol as the main constituent is preferred. Among these, polyesters mainly composed of polyethylene terephthalate and polyethylene naphthalate, copolymerized polyesters composed of terephthalic acid, 2,6-naphthalenedicarboxylic acid and ethylene glycol, and mixtures of two or more of these polyesters are mainly used. Polyester as a constituent component is preferable.

  The thickness of the film support according to the present invention is preferably 10 to 300 μm, more preferably 20 to 150 μm. The film support of the present invention may be a laminate of two sheets, and in this case, the type may be the same or different.

[Method for producing near-infrared reflective film]
In the method for producing a near-infrared reflective film of the present invention, a unit composed of a high refractive index layer and a low refractive index layer is laminated on a base material. Specifically, the high refractive index layer and the low refractive index are formed. It is preferable to form a laminate by alternately applying and drying the rate layer.

  Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or US Pat. Nos. 2,761,419 and 2,761,791. A slide bead coating method using an hopper, an extrusion coating method, or the like is preferably used.

  When the slide bead coating method is used, the viscosity of the high refractive index layer coating solution and the low refractive index layer coating solution in simultaneous multilayer coating is preferably in the range of 5 to 100 mPa · s, more preferably 10 to 10 mPa · s. The range is 50 mPa · s. Moreover, when using a curtain application | coating system, the range of 5-1200 mPa * s is preferable, More preferably, it is the range of 25-500 mPa * s.

  Further, the viscosity at 15 ° C. of the coating solution is preferably 100 mPa · s or more, more preferably 100 to 30,000 mPa · s, further preferably 3,000 to 30,000 mPa · s, and most preferably 10 , 30,000 to 30,000 mPa · s.

  As a coating and drying method, the high refractive index layer coating solution and the low refractive index layer coating solution are heated to 30 ° C. or higher, and then the temperature of the formed coating film is once cooled to 1 to 15 ° C. It is preferable to dry at 10 ° C. or higher, and more preferably, the drying conditions are wet bulb temperature 5 to 50 ° C. and film surface temperature 10 to 50 ° C. Moreover, as a cooling method immediately after application | coating, it is preferable to carry out by a horizontal set system from a viewpoint of the formed coating-film uniformity.

  In the present invention, when preparing the above-mentioned high refractive index layer coating solution, using an aqueous high refractive index layer coating solution prepared by adding and dispersing rutile type titanium oxide having a volume average particle size of 100 nm or less, It is preferable to form a high refractive index layer. At this time, the rutile type titanium oxide is added to the high refractive index layer coating solution as an aqueous titanium oxide sol having a pH of 1.0 or more and 3.0 or less and a positive zeta potential of the titanium particles. It is preferable to prepare.

[Application of near-infrared reflective film]
The near-infrared reflective film of the present invention can be applied to a wide range of fields. For example, pasting to facilities exposed to sunlight for a long time such as outdoor windows of buildings and automobile windows, film for window pasting such as heat ray reflecting film to give heat ray reflecting effect, film for agricultural greenhouse, etc. Used mainly for the purpose of improving weather resistance.

  In particular, the near-infrared reflective film according to the present invention is suitable for a member that is bonded to glass or a glass substitute resin base material directly or via an adhesive.

  The adhesive is placed so that the near-infrared reflective film is on the sunlight (heat ray) incident surface side when bonded to a window glass or the like. Moreover, when a near-infrared reflective film is pinched | interposed between a window glass and a base material, it can seal from surrounding gas, such as a water | moisture content, and is preferable for durability. Even if the near-infrared reflective film of the present invention is installed outdoors or outside the vehicle (for external application), it is preferable because of environmental durability.

  As an adhesive applicable to the present invention, an adhesive mainly composed of a photocurable or thermosetting resin can be used.

  The adhesive preferably has durability against ultraviolet rays, and is preferably an acrylic adhesive or a silicone adhesive. Furthermore, an acrylic adhesive is preferable from the viewpoint of adhesive properties and cost. In particular, since the peel strength can be easily controlled, a solvent system is preferable among the solvent system and the emulsion system in the acrylic adhesive. When a solution polymerization polymer is used as the acrylic solvent-based pressure-sensitive adhesive, known monomers can be used as the monomer.

  Moreover, you may use the polyvinyl butyral resin used as an intermediate | middle layer of a laminated glass, or ethylene-vinyl acetate copolymer type resin. Specifically, plastic polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., Mitsubishi Monsanto Co., Ltd.), ethylene-vinyl acetate copolymer (manufactured by DuPont, Takeda Pharmaceutical Co., Ltd., duramin), modified ethylene-vinyl acetate copolymer (Mersen G, manufactured by Tosoh Corporation). In addition, you may add and mix | blend an ultraviolet absorber, an antioxidant, an antistatic agent, a heat stabilizer, a lubricant, a filler, coloring, an adhesion regulator etc. suitably in an adhesion layer.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Production of near-infrared reflective film>
[Preparation of Sample 1]
(Preparation of coating solution for forming a high refractive index layer)
<Metal oxide particles for high refractive index layer: Preparation of titanium oxide sol>
In accordance with the following method, rutile type titanium oxide particles were prepared as metal oxide particles used for forming a high refractive index.

30 L of an aqueous sodium hydroxide solution (concentration 10 mol / L) was added with stirring to 10 L (liter) of an aqueous suspension (TiO ₂ concentration 100 g / L) in which titanium dioxide hydrate was suspended in water. The mixture was heated to 0 ° C. and aged for 5 hours, then neutralized with hydrochloric acid, filtered and washed with water. In the above reaction (treatment), titanium dioxide hydrate was obtained by thermal hydrolysis of an aqueous titanium sulfate solution according to a known method.

The base-treated titanium compound was suspended in pure water to a TiO ₂ concentration of 20 g / L, and 0.4 mol% of citric acid was added to the amount of TiO ₂ with stirring to raise the temperature. When the liquid temperature reached 95 ° C., concentrated hydrochloric acid was added to a hydrochloric acid concentration of 30 g / L, and the mixture was stirred for 3 hours while maintaining the liquid temperature to adjust the titanium oxide particles to 20% by mass. A titanium oxide particle sol was prepared.

  When the particle size of the obtained titanium oxide particle sol was measured with Zetasizer Nano manufactured by Malvern, the volume average particle size was 35 nm, and the monodispersity was 16%. Further, the titanium oxide particle sol is dried at 105 ° C. for 3 hours to obtain a particle powder, and X-ray diffraction measurement is performed using a JDX-3530 type manufactured by JEOL Datum Co., Ltd. to obtain rutile type titanium oxide particles. It was confirmed. Moreover, it was 2.76 as a result of measuring the refractive index of a rutile type titanium oxide particle using U-4000 type (made by Hitachi, Ltd.).

<Preparation of coating liquid 1 for forming a high refractive index layer>
While stirring 50 g (titanium oxide: 10 g) of the above-prepared titanium oxide particle sol, 1) HACP-01 (collagen tripeptide manufactured by Zerais Co., Ltd.) was dissolved in pure water at a concentration of 10% by mass as a water-soluble polymer. 30 g of gelatin solution 1 was added and then heated to 90 ° C. Stirring was continued while heating for 3 hours, and then the mixture was cooled to 50 ° C. Next, 2) 200 g of a 2.1% by weight gelatin solution 2 of P509 (gelatin treated pork skin acid gelatin) and Coatamine 24P (quaternary ammonium salt cationic surfactant, manufactured by Kao Corporation) as a surfactant 0.51 was added to prepare a coating solution 1 for forming a high refractive index layer.

(Preparation of coating solution for forming a low refractive index layer)
<Metal oxide particles for low refractive index layer: silicon oxide particles>
Snowtex OXS (Nissan Chemical Co., Ltd., colloidal silica, average particle size 4-6 nm) was used. The refractive index of the silicon oxide particles is 1.44.

<Preparation of coating solution 1 for forming a low refractive index layer>
In the preparation of the coating solution 1 for forming a high refractive index layer, instead of the titanium oxide particle sol, Snowtex OXS (Nissan Chemical Co., Ltd., colloidal silica, average particle size of 4 to 6 nm) is used as the particle mass so as to have the same amount. A coating solution 1 for forming a low refractive index layer was prepared in the same manner as described above.

(Measurement of refractive index of coating film)
Spin the prepared coating liquid 1 for forming a high refractive index layer and the coating liquid 1 for forming a low refractive index layer on a blue glass having a refractive index of 1.518 so that the film thickness after drying is about 1 μm. After coating with a coater, it was dried for about 5 minutes on a hot plate at 80 ° C.

  Subsequently, as a result of measuring the refractive index of the obtained high refractive index layer coating film and low refractive index layer coating film with F20 desktop film thickness measuring system (Filmmetrics film thickness refractive index measuring device), the high refractive index layer The refractive index of the coating film was 1.90, and the refractive index of the low refractive index layer coating film was 1.48.

  Subsequently, using the coating liquid composed of a water-soluble polymer prepared by removing each metal oxide particle from the coating liquid 1 for forming a high refractive index layer and the coating liquid 1 for forming a low refractive index layer, drying is similarly performed. It was 1.52 as a result of measuring the refractive index of a coating film (water-soluble polymer).

  That is, the high refractive index layer 1 is composed of water-soluble polymer having a refractive index of 1.52 and rutile titanium oxide particles (refractive index: 2.76), which are metal oxide particles having a higher refractive index. It was confirmed that it was configured.

  Similarly, the low refractive index layer 1 is composed of a water-soluble polymer having a refractive index of 1.52, and silicon oxide particles (refractive index: 1.44) which are metal oxide particles having a lower refractive index. It was confirmed that

  Moreover, the refractive index of each metal oxide particle was measured based on the B method (immersion method using a microscope (Becke's line method)) described in JIS K7142 “Plastic refractive index measurement method”.

(Formation of laminate)
(Formation of lower layer region)
<Formation of the first unit>
A wire bar was used on the condition that the dry film thickness was 161 nm on a polyethylene terephthalate film having a thickness of 50 μm heated to 45 ° C. while keeping the prepared coating solution 1 for forming a high refractive index layer at 45 ° C. Then, after setting the film surface by blowing cold air for 1 minute under the condition that the film surface is 15 ° C. or less, the hot air of 80 ° C. was blown and dried to form the high refractive index layer 1.

  Next, on the condition that the dry film thickness is 118 nm on the high refractive index layer 1 of the polyethylene terephthalate film heated to 45 ° C. while keeping the coating solution 1 for forming the low refractive index layer at 45 ° C., the wire bar Then, after setting the film surface by blowing cold air for 1 minute under the condition that the film surface is 15 ° C. or lower, the hot air of 80 ° C. is blown and dried to form the low refractive index layer 1. A first unit composed of a high refractive index layer 1 having a dry film thickness of 161 nm and a low refractive index layer 1 having a dry film thickness of 118 nm was formed.

<Formation of second to sixth units>
Similarly, on the first unit formed above, second to sixth units composed of a high refractive index layer 1 having a dry film thickness of 161 nm and a low refractive index layer 1 having a dry film thickness of 118 nm are formed, A lower layer region was formed.

  The total dry film thickness Σd1 of the formed lower layer region is 1675 nm.

(Formation of upper layer region)
<Formation of the seventh unit>
A wire bar was used under the condition that the dry film thickness was 161 nm on the sample on which the lower layer region heated to 45 ° C. was formed while keeping the prepared coating solution 1 for forming a high refractive index layer at 45 ° C. Then, after setting the film surface by blowing cold air for 1 minute under the condition that the film surface is 15 ° C. or lower, the hot air of 80 ° C. was blown and dried to form the high refractive index layer 7.

  Next, while keeping the coating solution 1 for forming a low refractive index layer at 45 ° C., coating is performed using a wire bar on the high refractive index layer 7 heated to 45 ° C. under the condition that the dry film thickness is 118 nm. Then, after setting the film surface by blowing cold air for 1 minute under the condition that the film surface is 15 ° C. or less, the film is dried by blowing hot air of 80 ° C. to form the low refractive index layer 7, and the dry film thickness A seventh unit composed of a high refractive index layer 7 having a thickness of 161 nm and a low refractive index layer 7 having a dry film thickness of 118 nm was formed.

<Formation of eighth to twelfth units>
On the seventh unit formed above, similarly, the eighth to twelfth units composed of the high refractive index layer 7 having a dry film thickness of 161 nm and the low refractive index layer 7 having a dry film thickness of 118 nm are formed, An upper layer region was formed to prepare Sample 1 which is a near-infrared reflective film.

  The total dry film thickness Σd2 of the formed upper layer region is 1675 nm, and Σd1 / Σd2 of Sample 1 is 1.00.

  In addition, the above-mentioned film thickness of each layer was calculated | required by cutting out the cross section of the sample 1 which formed all the units, and image | photographing and analyzing the cross section using the scanning electron microscope.

[Preparation of Samples 2 to 11]
In the preparation of the sample 1, the dry film thicknesses of the high refractive index layer and the low refractive index layer constituting the first to sixth units in the lower layer region and the high refraction constituting the seventh to twelfth units in the upper layer region. Samples 2 to 11 having Σd1 / Σd2 shown in Table 1 were prepared in the same manner except that the dry film thicknesses of the refractive index layer and the low refractive index layer were changed under the conditions shown in Table 1.

<< Measurement and evaluation of characteristic values of near-infrared reflective film >>
Measurements and evaluations were performed on the near-infrared reflectance of Samples 1 to 11 and the resistance to reflection unevenness of visible light, which were the produced near-infrared reflective films.

(Measurement of near infrared reflectance)
Using a spectrophotometer (using an integrating sphere, manufactured by Hitachi, Ltd., U-4000 type), the reflectance of each near-infrared reflective film in the region of 800 nm to 1300 nm is measured, and the average reflectance is obtained. Infrared reflectance was used.

(Evaluation of reflection light unevenness resistance of visible light)
Using a spectrophotometer (using an integrating sphere, manufactured by Hitachi, Ltd., U-4000 type), the reflectance of each near-infrared reflective film in the region of 380 nm to 780 nm is measured, and the maximum reflectance value (%) and the minimum The difference (%) from the reflectance value (%) was determined, and this was used as a measure for the reflection unevenness resistance of visible light. The smaller the numerical value, the smaller the difference in reflectance in the visible light region, and the less the reflection unevenness.

  The results obtained as described above are shown in Table 1.

  As is clear from the results shown in Table 1, the near-infrared reflective film having the layer structure defined in the present invention has a higher near-infrared reflectance and less reflection unevenness in the visible light region than the comparative example. I understand that.

  More specifically, when the near-infrared reflectance at 800 to 1300 nm is compared with the sample 1 of the comparative example in which Σd1 / Σd2 is 1.00, the sample 2 of the comparative example in which Σd1 / Σd2 is 1.9 or more and 3 shows that the near-infrared reflectivity of Samples 4 to 11 of Examples where Σd1 / Σd2 is 1.05 to 1.80 is high, while the near-infrared reflectivity of 3 is poor. Further, when attention is paid to the samples 9 to 11 of the example in which Σd1 / Σd2 is 1.05 to 1.25 times, it is understood that the reflection unevenness in the visible light region is further reduced. As a result of creating and evaluating a reflection spectrum at 380 nm to 1300 nm for each sample, the comparative example has a rectangular reflection peak at 800 to 1000 nm, but almost no near infrared reflection peak is observed at 1000 to 1300 nm. It was.

Example 2
[Preparation of near-infrared reflectors 4 to 11]
Near-infrared reflectors 4 to 11 were produced using the near-infrared reflective films of Samples 4 to 11 produced in Example 1. Near-infrared reflectors 4 to 11 were prepared by adhering the near-infrared reflective films of Samples 4 to 11 with an acrylic adhesive on a transparent acrylic resin plate having a thickness of 5 mm and 20 cm × 20 cm, respectively.

[Evaluation]
The produced near-infrared reflectors 4 to 11 of the present invention can be easily used in spite of the large size of the near-infrared reflector, and use the near-infrared reflective film of the present invention. As a result, excellent near-infrared reflectivity could be confirmed.

Claims (3)

A high refractive index layer containing a water-soluble polymer and metal oxide particles having a refractive index higher than the refractive index of the water-soluble polymer, a water-soluble polymer, and a refractive index of the water-soluble polymer. A near-infrared reflective film having a structure in which two or more layers are alternately laminated with low refractive index layers containing metal oxide particles having a refractive index lower than the refractive index,
The total number of layers of the high refractive index layer and the low refractive index layer is n, and the total film thickness of the constituent layers from the n / 2 region to the substrate is Σd1, the constituent layers from the n / 2 region to the outermost layer A near-infrared reflective film, wherein the film thickness ratio Σd1 / Σd2 is 1.05 or more and 1.80 or less, where Σd2 is the total film thickness.   The near-infrared reflective film according to claim 1, wherein the film thickness ratio Σd1 / Σd2 is 1.05 or more and 1.25 or less.   A near-infrared reflector comprising the near-infrared reflective film according to claim 1 or 2 on at least one surface side of a substrate.